Piston return mechanism



April 19, 1966 D. J. M INTOSH PISTON RETURN MECHANISM Filed Dec. 23, 1965 INYENTOR.

United States Patent 3,246,577 PESTON RETURN MECHANISM Donald 1. Macintosh, Rockford, lll., assignor to Sundstrand Corporation, a corporation of Illinois Filed Dec. 23, B63 Ser. No. 332,776 11 Claims. (Ci. 91-199) This invention relates to fluid pressure translating devices and especially relates to hydraulic pumps or motors of the reciprocating piston design. More particularly, this invention relates to piston return systems in such devices.

Hydraulic pumps and motors of the reciprocating piston type are well known to the art to be often usable as either pumps or motors. Among such devices are axial piston devices which include a drive shaft or driven shaft associated with either a cylinder block or an inclined or inclinable cam plate. In operation, relative rotational movement between the cylinder block and cam plate is produced by or produces rotation of the shaft. The cylinder block includes a plurality of reciprocating pistons in cylinders in annular array about the axis of the cylinder block. The pistons have inner ends disposed for reciprocation Within the cylinders and in a preferred form, outer ends adapted to bear against and transmit force to or receive force from the inclined cam plate through a slipper or shoe assembly, for example. Where the cylinder block is rotatable it includes passages from each cylinder to an end of the block for association with inlet and outlet passages in a port member which communicate successively with the passages from the cylinders upon relative rotation of the cylinder block with respect to the port member. The cylinder block is biased toward the port plate by pressure created during operation of the device, but it is also desirable to bias the cylinder block against the port member by independent means which supplements the operating pressure, e.g., during starting of the device. It is desirable to maintain contact between the reciprocating pistons and the inclined cam plate, and it is desirable to limit the amount of displacement of the piston bearing members from the cam plate to a preselected clearance of, e.g., a few thousandths of an inch.

It is a general object of this invention to provide a new and useful piston return system in a device of the character described.

It is a further object to provide new and useful means in a fluid translating device for biasing the cylinder barrel against the port member and for biasing the pistons toward the cam plate.

It is a more particular object of this invention to provide a system in accordance with the foregoing in which a resilient plate, such as a spring washer, e.g. a Belleville spring, functions to both bias the cylinder block against the port member and the pistons into operative association with the cam plate.

It is another object to provide such a system wherein the biasing means functions as a spacer member to limit the clearances in the device, e.g. between pistons and cam plate, to a small maximum value.

Still other objects will become readily apparent from the following detailed description taken in connection with the accompanying drawings in which:

PEG. 1 is a longitudinal section, taken along line 1-1 with respect to FIGS. 2 and 3, of a hydraulic fluid translating device incorporating an embodiment of the present invention;

3,246,577 Patented Apr. 19, 1966 FIG. 2 is a partial section taken along line 2-2 of FIG. 1; and

FIG. 3 is a partial section taken along line 3-3 of FIG. 1.

While an illustrative embodiment of the invention is shown in the drawings and will be described in detail herein, the invention is susceptible of embodiment in many different forms, and it should be understood that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illu trated. The scope of the invention will be pointed out in the appended claims.

Turning now to the figures, and especially FIG. 1, the embodiment illustrated is incorporated in an axial piston pump or motor. The pump includes a housing indicated generally at 10, having an end plate 11 removably secured thereto by bolts 12. Drive shaft 13 is rotatably supported at each end of housing 10 and extends through cylinder block 14. The bearings mounting shaft 13 in end plate 11 and the opposite end of housing 10 are each indicated by reference numeral 15 and retain shaft 13 against axial movement relative to housing it) and end plate 11.

Drive shaft 13 is drivingly connected as by splines 16 to a projection of cylinder block 14 for rotation of cylinder block 14 and drive shaft 13 together. The splined connection 16 includes cooperating splines on the drive shaft and cylinder block through which the drive shaft passes, and the splines may be slightly crowned longitudinally to permit tilting of the cylinder block at the splined connection, which allows for irregularities in the rotation of the cylinder block.

Cylinder block 14 includes an annular plurality of axially disposed cylinders within the cylinder block, each cylinder having an inner end of a piston 18 reciprocating therein. Cylinders 17 are provided with hearing inserts or bushings 19 within which the pistons reciprocate. Although it will be apparent that there are nine pistons in the annular series in the illustrated embodiment, any number of pistons and cylinders may be used, as is known to the art.

Cain plate 21 is mounted within housing 10' at one end of cylinder block 14 for pivotal movement about an axis transverse to and intersecting the axis of the drive shaft. The pivotal mounting of cam plate 21 is provided by trunnions (not shown) secured to housing 10 at opposite sides thereof to provide a pivotal axis of cam plate 21 generally normal to the plane of FIG. 1 and intersecting the shaft axis where the latter passes through the plane containing the centers of the spherical piston ends. The cam plate 21 is adapted to be pivoted about its axis at an incline in either direction with respect to a neutral center position for adjustment of displacement of the pistons 18 within the cylinder block cylinders 17. For this purpose projection 22 on cam plate 21 is provided to pivot the cam plate on its axis. The projection is accessible through opening 23 in the wall of housing 10 and may be linked to suitable actuating means connectible by means of bore 24 to control the inclination of cam. plate 21 as is well known.

The outer ends of pistons 18 are of spherical configuration and are universally connected to hearing members such as hearing shoes 25 which are adapted to slide upon thrust bearing member 26 which is supported on cam plate 21 and annularly slidable relative thereto. Bearing member 26 defines the bearing surface for shoes 25. Of course, other pistons within the pump are equipped with similar bearing shoes. Whenever any of pistons 18 is described in association with other members, it is to be understood that the remainder of the pistons 18 are also in association with similar or the same members.

A holddown member, such as ring 27, engages the bearing shoes 25 for carrying the bearing shoes in slidable contact with bearing surface 26. Holddown ring 27 is provided with a large central bore through which is mounted a collar 28 having an inner concave surface. The concave surface receives and is slidable pivotally over the spherical outer surface of a spherical extension or projection 29 of cylinder block 14, projection 29 and collar 28 forming the ball and socket respectively of a ball and socket joint. The collar 28 is pivoted on and piloted by projection 29 of cylinder block 14 for pivotal movement of collar 28 with respect to the block 14 and shaft 12 about the center of the collar which lies on the shaft axis approximately midway the spline connection and in the plane containing the pivotal centers of the universal connections of pistons 18 with shoes 25, i.e., the sphere centers of the ends of pistons 18.

Collar 28 includes an outwardly projecting flange 32 which engages one face of a resilient plate member of the form of an annular frusto conical Belleville spring 33. Collar 28 extends through the central opening of spring 33 and thence through the central opening of ring 27 and carries both spring 33 and ring 27 by flange 32 for movement with collar 28. Adjacent their central openings, ring 27 and spring 33 are in contact, but the surface of ring 27 tapers radially outwardly and away from contact with spring 33. Each of shoes 25 projects through aligned annular openings in spring 33 and ring 27, and each includes a flange 34 which engages the surface of ring 27, tending to hold [ring 27 into tight contact with spring 33 adjacent collar 28. Any force tending to pull shoe 25 from hearing plate 26 results in a force holding spring 33 grounded against collar 28 at ridge 32.

Radially of collar 28, where ring 27 is tapered away from spring 33, an annular array of bosses 35 is provided on the ring. Spring 33 is shown in FIG. 1 in its configuration under compression and appears as a generally flat member though in fact it may not be. It is held in its compressed form in the assembly by bolts 12 which hold end plate 11 against the open end of housing 10. In noncompressed form, spring 33 is disc-shaped, of slight frusto conical configuration, open C cross section. In FIG. 1, the spring 33 is positioned to bias between flange 32 and bosses 35, i.e., the base of the cone or the open position of the C configuration is to the right. The biasing of spring 33 acts in one direction to urge ring 27 (via bosses 35) to carry shoes 25 into facial engagement with hearing plate 26. In the other direction spring 33 urges block 14, including bearing plate 38 pinned thereto, into engagement with port plate 39. Port plate 39 is pinned at 40 to end plate 11.

Spring 33 also serves as a shim limiting the amount of clearance between shoes 25 and bearing member 25. As a shim, spring 33 functions to maintain bearing shoes 25 in close proximity with the bearing surface 26 of cam plate 21 without respect to any urging by spring 33. Thus, if spring 33 should become overpowered during operation of the device, e.g. by sticking of pistons within cylinder block cylinders or by momentary delay of the pistons being pulled from the cylinders upon a rapid increase in pump displacement, spring 33 still functions as a shim or spacer and prevents the withdrawal of the piston bearing members from the cam plate a greater distance than a minimum operating clearance. The minimum operating clearance is preselected and is provided during assembly of the device as elements are assembled from the left side of housing 10 with housing end plate 11 removed.

After the internal elements are assembled and placed in housing 10, end plate 11 is drawn into sealing peripheral attachment with housing 10. End plate 11 urges the cylinder block 14 and collar 28 against spring 33 which is in turn in position against bosses 35. The spring is loaded, i.e., placed under compression or tension, as bolts 12 are tightened. Shim means, e.g. in the form of a gasket 43, is provided to establish the desired or proper amount of loading of spring 33, gaskets of lesser thickness providing greater loading.

Cylinders 17 are provided with arcuate end ports 44 (FIG. 3) and bearing plate 38 includes complementary extensions 45 of ports 44 therethrough. The passage configuration, as viewed from either side of plate 38 is the same as the passage configuration on the end of cylinder block 14 as illustrated in FIG. 3. Plate 38 may include wear-resistant materials on its opposing surfaces and particularly on the surface facing port plate 39 or may be entirely of suitable bearing material such as bronze.

Port plate 39 includes arcuate inlet and outlet passages 47 and 48 passing therethrough for conducting fluid to and from passages 45 as cylinder block 14, including plate 38, is rotated. The general configuration of passages on both sides of port plate 39 is generally the same and is also generally the same as the configuration of passages leading to the inner face of housing end plate 11 as illustrated in FIG. 2. Port plate 39 may also have wears-resistant surfaces, such as hardened steel, especially facing cylinder block end plate 38.

Inlet and outlet passages 47 and 48 extend through housing end plate 11 to an inlet and an outlet (not shown) in the usual manner. The inlet and outlet are oonnectible to fiuid lines (not shown) for operation of the device as a pump or motor as will be readily apparent to those skilled in the art.

In operation of the device as a pump, shaft 13 and block 14 are rotated and fluid valved through port plate 39 and bearing plate 38 is drawn into the piston cylinders on the low pressure side or inlet side of port plate 39. The pistons 18 are sequentially withdrawn from cylinder 17 while riding up the incline of member 26 and then press bearing shoes 25 against the cam plate bearing member 26 while riding down member 26 as fluid is forced from the cylinder and from outlet 48. The annular series of cylinder block passages are successively brought into association with the low pressure or inlet passage and then with the high pressure or outlet passage in conventional manner as block 14 rotates. Also as the cylinder block rotates, bearing plate 38 slides against port plate 39 and is biased thereagainst by the force of pistons 18 reacting against cam plate 21 and by resilient plate 33 which is grounded through shoes 25 and bearing member 26 on the cam plate 21.

Additionally, shoes 25 slide around cam plate 21 on the cam plate bearing surface 26 and are urged or held against the bearing surface not only by the action of pistons 18 but also by resilient plate 33 grounded through collar 28, block 14 and plates 38 and 3-9 on end plate 11. Resilient plate 33, as a shim, prevents withdrawal of shoes 25 from surface 26 a greater distance than the minimum operating clearance between the shoes and cam plate surface. Thus spring 33 biases the piston ends against the cam plate and the cylinder block against the port plate. The shim or spacing function of spring 33 may permit use of a weaker spring for such biasing in that even severe stress on the spring means during the operation of the pump sufiicient to overpower the spring function of spring 33 cannot remove the shoes more than the minimum operating clearance provided by the shim.

It will be apparent to those in the art that the device, although its pump operation has been described, is also operable as a motor. Accordingly, high pressure fluid is charged to one of passages 47 or 48 and drained from the other to rotate block 14 and shaft 13 as an output shaft for conventional motor action of an axial piston motor. Spring means 33, in such operation, still functions to bias block 14 toward the port plate and shoes 25 against the cam plate.

Regardless of its intended operation as a pump or as a motor, it is apparent that, in the present invention, there has been provided a new and useful improvement in a fluid energy translation device which employs a resilient plate member for maintaining the cylinder block and piston bearing members or surfaces in effectively operative association with the remainder of the motor or pump assembly even during adverse conditions of operation.

I claim:

1. A fluid energy translation device including a cylinder block, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the block and with outer ends protruding from the block, an inclined cam plate facing said outer piston ends, a bearing surface on said cam plate, the outer ends of said pistons having bearing means being adapted to slidably follow said bearing surface, means mounting said cylinder block and cam plate for relative rotation, and inlet and outlet means communicating successively with ports from said cylinders upon relative rotation of the cylinder block and cam plate, the improvement which comprises a resilient disc biasing between the bearing means and said cylinder block for urging all of said bearing means in engagement with said bearing surface.

2. In a hydraulic fluid translation device including a housing with a closing end plate, a cylinder block rotatably mounted in said housing, a drive shaft adapted to drive or be driven by said rotatable cylinder block, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the block and protruding therefrom at one end of the block, an inclined cam plate facing said one end of said block, a bearing surface on said plate, the outer ends of said pistons having bearing means being adapted to slidably follow said bearing surface, a port member having inlet and outlet passages communicating successively with ports from said cylinders upon rotation of the cylinder block, and the improvement which comprises a generally disc shaped Belleville spring biasing all of said bearing means and said cylinder block for retaining said bearing means in engagement with said bearing surface and for biasing the other end of said cylinder block in facial engagement with said port member for communication of said passages with said ports from said cylinders.

3. The device of claim 2 including means universally connected to said piston ends and means including an annular array of bosses in pressing contact with said spring means for grounding said spring means against said universally connected means.

4. The device of claim 2 including shim means between the housing and closing end plate providing the proper tension in said spring means.

5. The device of claim 2 wherein said Belleville spring means is disposed as a shim between the cylinder block and said bearing means for limiting return of the piston outer ends under hi h severity operating conditions and defining a maximum limit of permissible clearance between piston outer ends and cam plate bearing surface.

6. The device of claim 2 wherein said cam plate is mounted for pivotal movement and said Belleville spring is pivotally mounted on said cylinder block for rotation therewith and for pivotal movement generally parallel with the pivotal incline of the cam plate bearing surface.

7. An axial piston hydraulic pump or motor device comprising a housing, a rotatable cylinder block mounted in said housing, an annular series of axially disposed cylinders within said block, a series of pistons having inner ends reciprocable within said cylinders, a drive shaft rotatably mounted in said housing extending through said cylinder block, a spline connection between the cylinder block and drive shaft, a cam plate mounted in said housing at one end of said cylinder block for pivotal movement about an axis transverse to and intersecting the axis of said drive shaft, said cam plate having a bearing face inclined to one end of the cylinder block, said pistons having spherical outer ends, a' series of shoes universally mounted on the spherical outer ends of the pistons and having a bearing face engaging the bearing face on said cam plate, ports communicating the cylinders with the opposite end of said cylinder block, a port plate in the housing having inlet and outlet passages adjacent the opposite end of the cylinder block communicating successively with said cylinder ports upon rotation of the cylinder block, ring-like resilient disc means biasing said heating shoes against said cam face, a spherical surface on said one end of said cylinder block, means mounting said disc means on said spherical surface for anchored pivotal movement, the center of the spherical surface and the pivot point of said disc being located at the approximate midpoint of said spline and falling upon the axis of said shaft at the point where the shaft axis pierces the plane containing the centers of the spherical piston ends, and openings in said disc means for extension of each piston and bearing shoe therethrough, said disc means being of suflicient spring strength to bias said shoes against said cam plate bearing face and to urge and maintain said cylinder block against the port plate against any counterforces present during normal low severity operation of said device and being disposed to maintain a maximum limit for the clearance between said engaging bearing faces.

8. An axial piston hydraulic pump or motor device comprising a housing, a cylinder block rotatable in the housing and having an annular series of axially disposed cylinders each with a reciprocable piston therein having a spherical outer end, a drive shaft rotatable in the housing and spline connected to the cylinder block adjacent the spherical piston ends, a cam plate in the housing having an inclined bearing face, bearing shoes respectively universally attached to the spherical piston ends and engaging the bearing face of the cam plate, ports communicating the cylinders with the end face of the block remote from the cam plate, a port plate in the housing having inlet and outlet ports communicating successively with the cylinder ports on rotation of the block, and piston return means including a spherical projection on the end of the cylinder block adjacent the spline connection, an annular collar seated on the spherical projection and having an outwardly extending flange, an annular holddown ring engaging the bearing shoes, and an annular frusto-conical spring member having its base disposed toward the cam plate, an outer portion engaging the holddown ring, and an inner portion engaging the collar flange to bias the bearing shoes against the cam bearing face and the cylinder block against the port plate.

9. The device of claim 1 wherein said resilient disc is disposed as a shim between the cylinder block and said bearing means for limiting the return of the piston outer ends and defining a maximum limit permissible clearance between the piston outer ends and the cam plate bearing surface.

10. A fluid energy translation device comprising; a cylinder block, a drive shaft connected for rotation with said cylinder block, a plurality of pistons with inner ends disposed in reciprocation within cylinders in the block and with outer ends protruding from the block, an inclined plate facing said piston outer ends, a bearing surface on said cam plate, the outer ends of said pistons having hearing means being adapted to slidably follow said bearing surface, means mounting said cylinder block and said cam plate for relative rotation, inlet and outlet means communicating successively with ports from said cylinder upon relative rotation of the cylinder block and cam plate, the improvement which comprises a generally annular resilient disc surrounding said drive shaft and biasing all of said bearing means, said resilient disc being generally parallel with said cam surface and adjacent thereto, said disc extending generally radially outward at least to said bearing means.

11. The device of claim 10 and further including a holddown ring directly engaging all of said piston bearing means, said resilient disc Zngaging said holddown ring 2,776,627 1/1957 Kee1 7460 and urging said ring into engagement with said piston 3,169,488 2/1965 Galliger 9257 bearing means FOREIGN PATENTS References Cited by the Examiner 5 627,658 9/ 1961 Canada.

UNITED STATES PATENTS SAMUEL LEVINE Primary Examiner. 2445281 7/1948 Rystrom 91175 P. E. MASLOUSKY, Assistant Examiner,

2,667,862 2/1954 Muller 91199 

1. A FLUID ENERGY TRANSLATION DEVICE INCLUDING A CYLINDER BLOCK, A PLURALITY OF PISTONS WITH INNER ENDS DISPOSED FOR RECIPROCATION WITHIN CYLINDERS IN THE BLOCK AND WITH OUTER ENDS PROTRUDING FROM THE BLOCK, AN INCLINED CAM PLATE FACING SAID OUTER PISTON ENDS, A BEARING SURFACE ON SAID CAM PLATE, THE OUTER ENDS OF SAID PISTONS HAVING BEARING MEANS BEING ADAPTED TO SLIDABLY FOLLOW SAID BEARING SURFACE, MEANS MOUNTING SAID CYLINDER BLOCK AND CAM PLATE FOR RELATIVE ROTATION, AND INLET AND OUTLET MEANS COMMUNICATING SUCCESSIVELY WITH PORTS FROM SAID CYLINDERS UPON RELATIVE ROTATION OF THE CYLINDER BLOCK AND CAM PLATE, THE IMPROVEMENT WHICH COMPRISES A RESILIENT DISC BIASING BETWEEN THE BEARING MEANS AND SAID CYLINDER BLOCK FOR URGING ALL OF SAID BEARING MEANS IN ENGAGEMENT WITH SAID BEARING SURFACE. 